The supply of therapeutic oxygen to patients in homes and other residential settings is an important and growing market in the health care industry. A segment of this market includes the development and commercialization of portable oxygen concentrators, particularly units that can be carried easily by patients requiring continuous oxygen therapy. A portable and easily-carried oxygen supply may be provided by stored liquid or compressed oxygen with an appropriate vaporization or pressure regulation system and a gas delivery cannula. Alternatively and preferably, oxygen may be supplied by a small air separation device carried by the patient that supplies gaseous oxygen at the desired purity, flow rate, and pressure. Power for operating the device can be provided by a rechargeable power supply, typically a rechargeable battery. The small air separation device may be an adsorption-based system using a pressure swing adsorption (PSA) process.
Respiratory oxygen usage rates typically range up to about 5 lpm (liters per minute at 23° C. and 1 atma pressure) for ambulatory patients with moderate oxygen requirements. The design of an easily-carried, rechargeable, portable oxygen concentrator in this product range should achieve an appropriate balance among product gas flow rate, weight, and power supply life or run time (i.e., the operating time between power supply recharges). This balance requires the proper choice of numerous operating and design parameters and presents a significant challenge to engineering designers. In a small adsorptive air separation unit, for example, design parameters may include product purity, product delivery pressure, type of process cycle, process cycle pressure envelope, adsorbent, number and dimensions of adsorbent beds, type of gas mover, type of power supply, gas flow control methods, electrical control systems, and materials of construction.
There is a need in the art for methods to design portable adsorption-based oxygen generation systems that provide the required gas supply rates and run times with minimum system weight. This need can be met by optimization methods that enable designers to balance these requirements while specifying appropriate process and mechanical parameters for these systems.